Adult neurogenesis: a compensatory mechanism for neuronal damage

It is now evident that the adult vertebrate brain including the human brain is efficiently and continuously generating new neurons. In the first part we describe the current view of how neurons are generated in the adult brai n and the possible compensatory reactions to pathological situations in whi ch neuronal damage might stimulate neural stem cell activity. In the second part, we discuss the current knowledge on the signals and cells involved i n the process of neurogenesis. This knowledge is important because any neur onal replacement strategy depends on our ability to induce or modulate each step on the way to a new neuron: stem cell proliferation, cell fate determ ination, progenitor migration, and differentiation into specific neuronal p henotypes. Identification of the molecular signals that control these event s are essential for the application of neural stem cell biology to develop repair strategies for neurodegenerative disorders.